Comparison of the efficiency of plastic nets for shading greenhouse in different climates.

In order to limit the internal air temperature during summer and create optimum cultivation conditions in the greenhouses, a common solution utilized by growers is the shading against excessive solar radiation using plastic nets; this is due to their photo-selective properties. With the aim to analyse the efficacy of the shading effect of plastic nets in different climates, experimental trials have been carried out on some identical small-scale tunnels installed in two different locations, one in Mediterranean area (Acerenza - Southern Italy) and one in arid conditions (Riyadh - Saudi Arabia). These tunnels have been covered with a plastic film and shaded with a white plastic net installed either in contact or at a distance of 20 cm over the cladding film. The radiometrical characteristics of the plastic film and nets have been determined through laboratory tests, while the internal microclimatic conditions have been monitored inside these experimental tunnels in both locations. The results obtained enabled to start a comparative analysis of the performance of the tested nets, highlighting the role that a selective filtering of the solar radiation may play on limiting high temperatures and on the quality of the incoming light.